None are involved in this invention.
1. Field of the Invention
The field of this invention is structural units, particularly that of folding structural units.
2. Background of the Invention
Many fold-up frames are known, but none has been found which unfolds from a parallel bundle of four frame posts automatically and co-dependently into a square, planar frame, and back again.
Four substantially identical frame posts are formed with hinge halves at each end. The hinge halves are positioned orthogonally to one another as viewed along the longitudinal axis of each frame post. Each hinge half defines a hinge-edge position for a hinge pin such that the longitudinal axis of the hinge pin forms an angle with the longitudinal axis of the frame post which is substantially 125.7xc2x0, or the complementary angle, 54.3xc2x0 (plus or minus one-half degree).
When hinged together the four frame posts form a square, and, pivoting about their respective hinge axes, they fold up into a parallel bundle.
It may be noted that the frame post and hinge assembly of the present invention is somewhat similar to the structure disclosed in my copending application Ser. No. 09/022,552, International Publication No. 99/41943, in FIGS. 5a, 5b, and 5c thereof.
The foregoing description is conceptually simple and works well enough when paper models or fairly flexible materials are used to construct the folding frame of my invention (e.g. for a fold-up kite or the like). It can also be pertinent in applications which do not require folding to the parallel position. With more rigid versions of the invention, designed to carry more substantial loads, the rigid frame posts have sufficient bulk as to interfere with one another when closing to the parallel position. Therefore, to achieve the parallel configuration, practical considerations require that the hinge halves be so formed as to have the hinge pin axis offset from the longitudinal axis of the frame posts. If a frame post were constructed with aluminum tubing of one inch outside diameter, then the offset of the hinge pin axis would have to be at least one-half inch, i.e., at least half the diameter of the frame post.
Each frame post has a hinge half angled acutely to the frame post at a first end while the hinge half at the second end is angled obtusely to the frame post (or, in other words, the second end is angled acutely to the extended axis of the frame post.) In the general case, all half hinge edges (or hingepin axes) are offset from the longitudinal axis of the frame post with the offset to the inside of the folding framework (as is best observed when the four frame posts are in the parallel bundle configuration) and the hingepin axes of the hinge halves at each end of the frame posts are orthogonal to one another as viewed along the axes of the frame posts.
Since, with respect to any two nonparallel lines such as those containing the axes respectively of the frame post and of the hingepin, each of which has an infinite number of planes passing through it, exactly two such planes exist which are parallel to one another, one including the line of the first axis (e.g., frame post) and the other including the line of the second axis (e.g., hingepin). So, with respect to the two planes which are parallel to one another and which include respectively the axis of the frame post and the axis of the offset hinge-pin, the angle formed between those two axes when viewed orthogonally to the two parallel planes, is substantially 125.7xc2x0, or the complementary angle, 54.3xc2x0 (plus or minus one-half degree).
The hinges are connected to form the four frame posts into a square, or as folded, into a parallel bundle. Each frame post must be either the same length with hinges at the ends, or at least have the longitudinal separation of the hinge halves be of the same length for all of the four frame posts which are to be joined together. Under an applied force and pivoting now about their respective hingepins, the frame posts rearrange themselves, and the structure which they form, from a parallel bundle, and then through an intermediate hyperbolic paraboloid phase and then into a planar square frame, which is perpendicular to the axes of the parallel bundle.
When any frame post is moved relative to its neighbor frame post, beginning from the parallel bundle configuration, in which the angle between each frame post and its pivotal neighbor is zero, the angle between each frame post and its neighbor increases such that that angle is the same at each symmetrically opposed corner of the frame for each corner at each intermediate unfolding stage. If the four respective corners of the frame are identified in series around the frame as a, b, c, and d, then a and c are symmetrically opposed and b and d are symmetrically opposed. Furthermore, a force applied at any point along any of the frame posts to change the separation of that post with respect to another post, is immediately and equally transmitted to all other frame posts in the framework. This, of course, assumes that the frame posts are constructed of a torsionally stable material, for example, aluminum tubing. Linked together as they are by the four respective hinge-pins, none of the four frame posts is free to move without there being a corresponding movement of each of the other frame posts.
Thus, if one corner is mounted to an external structure, and is therefore constrained against movement with respect to its corresponding hingepin axis, a coordinated force applied to drive apart the two frame posts forming the mounting corner will cause the folded frame to unfold in a uniform manner, each corner having the same angle as its symmetrically opposed corner at any given point during the excursion.
Should the mounted corner be affixed to another structure, such as a mounting column, or a building, then my frame can be made to fold or unfold adjacent to that mounting structure. If the frame is made to stretch awning canvas, the frame makes a sturdy side-mount umbrella which can be furled or unfurled as one may wish.
Minor changes may be made to the configuration especially to effect stable drive mechanisms. Slight variations may be necessary, and one such is described below with respect to the preferred embodiment.